1977 Evinrude 85 hp Bogs down after 10min full throttle

[Kevin Hedlund]

I have a 1977 Evinrude 85 hp Bogs down after about 10min full throttle. Carbs are clean, primer bulb is hard and it doesnt help when i pump it again.

 

[Kevin Hedlund]

When i was out on the lake i put my hand on the head and wouldn't burn my hand at all. So does the engine kill one of the cylinders when it overheats? The model number 85799s. It was running fine last year. I have a temp gun i can use to check the temp on the heads. What kind of temp am i looking for?

 

[racerone]

The powerpack on a 77 Evinrude is not connected to the battery.------It is a magneto system.

 

[Kevin Hedlund]

The RECTIFIER was shorting out and killing the motor last year so i removed it. I charge the batteries after every time i go out to the lake

 

[Kevin Hedlund]

I forgot to say it was running but just had no power nothing at full throttle.

 

[racerone]

Do a compression test.----------Were the highspeed jets removed from the side of the carburetor float bowls for inspection.---------Alcohol in fuel may attack old rubber hoses and block fuel flow.----Best to replace hoses on the motor with newer type hoses.

 

[daninbuffalo]

I am new to power boating, but I had a similar problem because I did not open the vent on my fuel tank.

 

[coupee]

the gas tank pickup tube may be restriced try a different tank .are you using a built in tank? check screen in tank. if you used ethy alcohol gas your filter screens are pluged.

 

[hasbeen]

Had a similar situation with my '76 J115. Ran great for a while then would lose what seemed like about 50% power. I'd remove the cover to look for problems, find nothing obvious, replace the cover and it would do the same (run good briefly) thing again. Turned out to be bad coils/wires------after it had run long enough to build some heat and humidity under the cowl, sparks would start going to inappropriate places. Replaced the coils and never had the problem again.